1. Field of the Invention
The present invention relates to storage apparatuses, and, more particularly, to a technique for interconnecting a controller of a storage apparatus to each unit.
2. Description of the Related Art
Storage apparatuses are used to store or read out data on or from a memory such as a hard disk drive (HDD), and include a control unit for controlling the entire processing of the storage apparatus and a storage unit for storing data. Furthermore, storage apparatuses include a power supply unit, a fan unit, and a thermometer unit which are used to maintain the environment of the storage apparatus.
Protocols for interfaces of storage apparatuses include the SAS (Serial Attached SCSI) protocol. In the SAS protocol, an expander unit functions as a relay between a controller unit of a storage apparatus and each of many units. An expander unit is connected to a storage unit, a PSU (Power Supply Unit), a fan unit, and a thermometer unit, and acquires environmental information (status information) from each of the PSU, the fan unit, and the thermometer unit every predetermined point in time. If the expander unit detects a change in the environmental information of any one of these units, the expander unit transmits the detection result to a controller unit. The controller unit checks the state of a corresponding unit each time it receives a notification that an unusual change in environmental information has occurred from the expander unit compliant with the SAS protocol. For example, if there is a poor contact at a connector of a unit, an abnormal state and a normal state may be repeated in accordance with the vibration of a storage apparatus.
If the change in environmental information often occurs, the expander unit transmits a notification about the occurrence of the change to the controller unit each time the change occurs. The exchange of environmental information between the controller unit and the expander unit and the exchange of data between each storage unit and the controller unit which the storage apparatus performs so as to store or read out data in or from a corresponding storage unit are performed via the same transmission line. Accordingly, many exchanges of environmental information between the controller unit and the expander unit interfere with the transmission of data between the controller unit and the expander unit which the storage apparatus performs so as to store or read out data in or from a corresponding storage unit.
Known techniques are disclosed in Japanese Unexamined Patent Application Publication Nos. 9-508990 and 9-259050.